1. Field of the Invention
The present invention relates to a wire feeding device for use in, for example, a harness manufacturing apparatus for manufacturing harnesses having a predetermined length.
2. Description of the Related Art
FIGS. 23 and 24 are schematic side views of a conventional harness manufacturing apparatus. By this harness manufacturing apparatus, a wire 30 intermittently fed by a wire feeding device A is subjected to various processing described later, so that harnesses of predetermined length, at both ends of which terminals 52 are press-clamped, are successively manufactured. This harness manufacturing apparatus includes the wire feeding device A, draw roller 11, front side clamp 12, cutter group 13, and rear side clamp 14.
A measuring roller 1 and feeding roller 2 are rotatably connected to the wire feeding device A, and both rollers 1 and 2 are arranged such that they can be rotated through a power transmission mechanism (not shown) in the same direction by the same amount of rotation synchronously with each other. A presser roller 4 pushed to a side of measuring roller 1 by a spring 3 is provided close to measuring roller 1. Spring 3 and presser roller 4 are also provided for a side of feeding roller 2.
As shown in FIG. 25, this harness manufacturing apparatus is provided with not only a roller drive device 22 to drive measuring roller 1 but also another drive device 23 to drive draw roller 11, clamps 12 and 14, cutter group 13 and the like, respectively. A control apparatus 20 to control these drive devices 22 and 23, and an input device 31 to input various commands and information to control apparatus 20 are provided.
A covered wire 30 pulled out from a stock reel (not shown) is inserted between measuring roller 1 and presser roller 4 and wound around measuring roller 1 and feeding roller 2. Wire 30 wound around measuring roller 1 and feeding roller 2 forms an S-shape. Covered wire 30 is then inserted between draw rollers 11, front side clamps 12, cutters 13, and rear side clamps 14, respectively.
After wire 30 has been set in the aforementioned manner, the information of predetermined length (a wire feeding amount) is inputted into control apparatus 20 through input device 31, so that an operation start command is given to control apparatus 20. Then wire 30 is held by both clamps 12 and 14, and group cutters 13 are synchronously operated. As a result of the foregoing, wire 30 is cut by a disconnecting cutter 13a disposed in the center of cutter group 13, and at the same time outer circumferential covered portions of wire 30 are notched by notching cutters 13b provided on both sides of the cutter group 13. When front side clamp 12 is moved under the aforementioned notched condition of wire 30, wire 30 held by clamp 12 (this wire 30 will be referred to as "a residual wire 30", hereinafter) is moved in the direction of arrow Q in the drawing. As a result, the covered portion at the end of residual wire 30 is peeled. Rear side clamp 14 is concurrently moved in the direction of arrow P, so that the covered portion at the end of the wire 30 held by clamp 14 (this wire 30 will be referred to as "a cut wire 30", hereinafter) is peeled.
Successively, residual wire 30 is moved in a direction perpendicular to the surface of FIG. 23 together with front side clamp 12, and a terminal 52 (shown in FIG. 24) is press clamped to the peeled end portion of residual wire 30 by a terminal press-clamping device (not shown). Front side clamp 12 then returns to the initial position.
On the other hand, rear side clamp 14 is moved in a direction perpendicular to the surface of FIG. 23, and a terminal is press clamped to the peeled portion of cut wire 30 by a terminal press-clamping device (not shown). Then, rear side clamp 14 discharges cut wire 30 to a predetermined discharge position and returns to the initial position.
After both clamps 12 and 14 have been released, measuring roller 1 and feeding roller 2 are rotated by a predetermined number of revolutions so that wire 30 is fed to the draw roller 11 side by a feeding amount corresponding to the predetermined cutting length. After the wire feeding motion, draw roller 11 is rotated so that wire 30 is sent to the rear clamp 14 side as shown in FIG. 23.
After a one-cycle operation has been completed in this manner, the aforementioned motions are repeatedly carried out so that cut wires (harnesses), in which terminals 52 are press clamped to the peeled end portions, are successively manufactured.
As shown in FIG. 26, a relation between the number of revolutions of measuring roller 1 and the substantial feeding amount of wire 30 per one cycle is expressed by the equation L.sub.r =2.pi.R.sub.30 X where the number of revolutions of measuring roller 1 is X, the substantial feeding amount of wire 30 is L.sub.r, and the radius of curvature of the core wire center C.sub.30 of wire 30 wound around measuring roller 1 is R.sub.30.
On the other hand, in the aforementioned harness manufacturing apparatus, the number of revolutions X of the measuring roller 1 is calculated in the following manner: the radius of curvature of the center of the wire, which is used as a reference radius and has been set in the wire feeding device A (this radius of curvature is referred to as "reference radius of curvature R.sub.s ", hereinafter), is determined from measured data; the reference radius of curvature R.sub.s is assumed to be the radius of curvature of all the wires to be processed, and the number of revolutions X is calculated in accordance with the reference radius of curvature R.sub.s. That is, the number of revolutions X of measuring roller 1 is calculated according to the equation L.sub.h =2.pi.R.sub.s X where the predetermined cutting length (the feeding amount) inputted into control apparatus 20 is L.sub.h, and measuring roller 1 is rotated by this feeding amount.
However, as shown by an imaginary line in FIG. 27, when a wire 30a is fed, the radius of curvature R.sub.30a of which is different from the reference radius of curvature R.sub.s, in the case of the aforementioned wire feeding device A, the number of revolutions X is found from the equation L.sub.h =2.pi.R.sub.s X). The substantial feeding amount L.sub.r of the wire fed by the number of revolutions X is 2.pi.R.sub.30a X. As described above, the radius of curvature R.sub.s is different from R.sub.30a. Therefore, the substantial feeding amount L.sub.r (=2.pi.R.sub.30a X) of wire 30 is different from the predetermined feeding amount L.sub.h (=2.pi.R.sub.s X). This difference causes a number of problems.
In the case where a wire is used, the diameter of which is larger than that of the reference radius of curvature R.sub.s, the substantial feeding amount becomes larger than the predetermined feeding amount. On the other hand, when the diameter of the wire is smaller than that of the reference radius of curvature R.sub.s, the substantial feeding amount becomes smaller than the predetermined feeding amount. Therefore, the feeding accuracy is deteriorated due to the difference of radius of curvature.
It is possible to correct the error caused between the predetermined feeding amount and the substantial feeding amount by the hand work of an operator using a trial-and-error method. However, it is necessary to conduct this correction work each time the type of wire is changed. As a result, the preparation work to change the type of wire is complicated.